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Combined heating & cooling - Heat pump - Ground-source - Office / Canada
Case study assignment
You have been hired by a small municipality in southern Manitoba to determine if it makes sense to heat and cool the community hall with a ground source heat pump (GSHP) system, which happens to be next to the hockey arena that already uses a GSHP system to make ice.
Site information
The closest applicable weather station is in the provincial capital of Winnipeg. The community hall is a single story building with a floor area of 929 m2. Constructed in 1974, it has relatively low insulation levels and an average number of windows. Electric space heaters provide most of the space heating and standard DX rooftop units provide ventilation make up air and air-conditioning. The hall is used for community functions and meetings and is often rented out for private functions. Most of the use is in the daytime and the equipment and lighting use for the building is relatively low. The hall has 2,000 m² of land available for the GSHP system installation. The soil at the site is primarily damp clay and the mean earth temperature is reported to be about 5.5 °C with an annual amplitude of 20 °C.
Manitoba is currently supplying 98.5% of its electricity generation with hydro and the remainder split among natural gas and coal.
Financial information
Eighty percent of the cost will be paid for in debt at an interest rate of 9% over a 20-year term. The discount rate used by the town is 10% and the inflation rate is 2%. Fuel costs are expected to rise at roughly a half-point above the inflation. The financial analysis should be performed over 25 years. Currently, the municipality pays 6¢/kWh for electricity, without a demand charge for the facility.
The heat pumps are estimated to cost about $235/kW (based on cooling capacity) and their compressors are expected to last 20 years before needing replacement. The existing conventional air-conditioner is estimated to have a remaining life of 10 years. A similar new air-conditioner would cost about $8,000. Drilling and grouting is estimated at $14/m of borehole.
Prepare a RETScreen study, document any assumptions that you are required to make and report on the significant conclusions from this analysis.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
Real project
Results
In 1998, the town of Miami, Manitoba, which is located about 100 km south-west of Winnipeg, initiated a project to install ground-source heat pump (GSHP) systems for making ice at the hockey arena and for heating and cooling the adjacent community hall.
The ice arena heat pumps were installed as a part of the first work phase. They include one low temperature heat pump for cooling the ice surface and two 5-ton heat pumps for heating the locker rooms and other conditioned areas of the arena. The second phase, which is described here, was initiated in 1999 and includes the installation of heat pumps to serve the community hall. Additional GSHP capacity for ice making for the arena is to be installed in a third phase of the project.
System description
The community hall GSHP system consists of two 10-ton heat pumps connected to a ground source heat exchanger (GHX) that uses a water/methanol mix as the working fluid. The ground heat exchanger is installed in a field of 48 boreholes, each 10 cm in diameter and 38 m deep. To limit pumping power, the borehole field is segmented to match the loads. For example, when ice making is not needed, only the heating and cooling segment of the GHX is utilized to meet the space heating or cooling loads.
During winter operation, the ice making system is rejecting heat to the ground while the space heating heat pumps are drawing heat from the ground. This boosts the efficiency and performance of both heat pumps systems.
Lessons learned
The big picture
Ground source heat pumps serving municipal government facilities such as community halls and ice skating and curling arenas are making inroads into the municipal facility market. For example, for arena applications these systems do not have the high annual start-up and shutdown costs associated with conventional ammonia ice-making plants and do not need the specialized expertise to operate them. When the GSHP system also provides space conditioning of adjacent buildings, the overall system's financial performance is improved even further.
Photo
Community hall - Heat pump - Ground-source, Manitoba, Canada
References
Case study assignment
You have been hired by a small municipality in southern Manitoba to determine if it makes sense to heat and cool the community hall with a ground source heat pump (GSHP) system, which happens to be next to the hockey arena that already uses a GSHP system to make ice.
Site information
The closest applicable weather station is in the provincial capital of Winnipeg. The community hall is a single story building with a floor area of 929 m2. Constructed in 1974, it has relatively low insulation levels and an average number of windows. Electric space heaters provide most of the space heating and standard DX rooftop units provide ventilation make up air and air-conditioning. The hall is used for community functions and meetings and is often rented out for private functions. Most of the use is in the daytime and the equipment and lighting use for the building is relatively low. The hall has 2,000 m² of land available for the GSHP system installation. The soil at the site is primarily damp clay and the mean earth temperature is reported to be about 5.5 °C with an annual amplitude of 20 °C.
Manitoba is currently supplying 98.5% of its electricity generation with hydro and the remainder split among natural gas and coal.
Financial information
Eighty percent of the cost will be paid for in debt at an interest rate of 9% over a 20-year term. The discount rate used by the town is 10% and the inflation rate is 2%. Fuel costs are expected to rise at roughly a half-point above the inflation. The financial analysis should be performed over 25 years. Currently, the municipality pays 6¢/kWh for electricity, without a demand charge for the facility.
The heat pumps are estimated to cost about $235/kW (based on cooling capacity) and their compressors are expected to last 20 years before needing replacement. The existing conventional air-conditioner is estimated to have a remaining life of 10 years. A similar new air-conditioner would cost about $8,000. Drilling and grouting is estimated at $14/m of borehole.
Prepare a RETScreen study, document any assumptions that you are required to make and report on the significant conclusions from this analysis.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
- Greenhouse gas (GHG) reductions are low because it is assumed that the existing grid mix is the base case electricity system in Manitoba, where most of the electricity generation is from hydroelectric facilities. However, since the GSHP requires less energy than conventional electric resistance heating systems and air-conditioners, it increases the potential for the local utility to sell its cleaner surplus electricity to neighbouring utilities that might have more GHG emissions per unit of electricity production (e.g. coal plants in Ontario).
- No initial cost credits are available since this is a retrofit situation where the GSHP is replacing an electric heating and cooling system that does not need to be replaced.
- The model calculates a large electricity saving. Significant demand savings are typical for GSHP systems as compared to conventional electric resistance heating and represent a benefit for the utility and the building owner. Financial credit for this savings depends on the electrical rate structure available to the facility.
- A tax analysis is not included because municipal facilities generally do not pay income or property taxes.
Real project
Results
In 1998, the town of Miami, Manitoba, which is located about 100 km south-west of Winnipeg, initiated a project to install ground-source heat pump (GSHP) systems for making ice at the hockey arena and for heating and cooling the adjacent community hall.
The ice arena heat pumps were installed as a part of the first work phase. They include one low temperature heat pump for cooling the ice surface and two 5-ton heat pumps for heating the locker rooms and other conditioned areas of the arena. The second phase, which is described here, was initiated in 1999 and includes the installation of heat pumps to serve the community hall. Additional GSHP capacity for ice making for the arena is to be installed in a third phase of the project.
System description
The community hall GSHP system consists of two 10-ton heat pumps connected to a ground source heat exchanger (GHX) that uses a water/methanol mix as the working fluid. The ground heat exchanger is installed in a field of 48 boreholes, each 10 cm in diameter and 38 m deep. To limit pumping power, the borehole field is segmented to match the loads. For example, when ice making is not needed, only the heating and cooling segment of the GHX is utilized to meet the space heating or cooling loads.
During winter operation, the ice making system is rejecting heat to the ground while the space heating heat pumps are drawing heat from the ground. This boosts the efficiency and performance of both heat pumps systems.
Lessons learned
- The costs of this retrofit installation were significantly higher than for a new construction project.
- Gains in performance and cost savings were achieved by using GSHP for both ice making and space heating/cooling. This helped maximize the financial returns of the project.
- The new ice making equipment significantly increased the operating season for the arena, which previously relied on ambient conditions to make ice.
- Local contractors can adequately service the system (rather than refrigeration specialists as required for a conventional ammonia ice making plant).
The big picture
Ground source heat pumps serving municipal government facilities such as community halls and ice skating and curling arenas are making inroads into the municipal facility market. For example, for arena applications these systems do not have the high annual start-up and shutdown costs associated with conventional ammonia ice-making plants and do not need the specialized expertise to operate them. When the GSHP system also provides space conditioning of adjacent buildings, the overall system's financial performance is improved even further.
Photo
Community hall - Heat pump - Ground-source, Manitoba, Canada
References
- Kemp, Steve, "Personal communication," Enermodal Engineering Ltd., 2002.
- Natural Resources Canada, South-Western Manitoba Town Simplifies Ice-making While Reducing Costs, Ottawa, Canada, 1999.
